When you search using an internet search engine like Google, search engines have databases filled with web pages that have been crawled by robots. The robots gather information from web servers and analyze the content to create searchable indexes. Search engines return results based on matches between your search terms and the indexes. There are two main types of search engines - robot-driven search engines that use robots to automatically crawl and index web pages, and directory search engines that are manually constructed indexes of websites. You can use search engines to find websites on topics you input through keyword searches or browsing categories.

1. How Internet Search Engine Work
● Database
● Google search
● Type of search engine
● How to use search engines

2. Database
● The database is
searched based on
the criteria you've set.
● Each search engine
return results in a
different way.
● Some search engine
results show URL that
the document,or the
first sentences of the
document.

3. Google Search
● When you search using
Google, google's web-
crawling robot,called
googlebot, sends a
requests to a web
server to gather the raw
material.
● Googlebot runs on
many computers at the
same time and
constantly requests and
receives web page.

4. Type Of Search Engine
Robot-driven Search Engine
The robot that is called the crawler and Spider goes round the WEB page in the Internet and collects data, and the data accumulates
in the data base. A lot of information that exists in WWW can be efficiently collected. Information of collected pages is analyzed
beforehand, and made the index.
Directory Search Engine
This is a server and a system that retrieves in the web directory manually constructed. A high-quality Web site can be retrieved
because it manually constructs it. There is a feature that it searches easily from the list of the retrieval result for a target site because
the outline of the site is manually filled in. However, there is a fault that there are not a lot of numbers of sites to be retrieved to input the
site to be retrieved manually.
Figure 1. Robot-driven Search Engine and Directory Search Engine Figure 2. The Mechanism of Robot-driven Search Engine

5. How To Use Search Engines
● Transfer guide
● Commodity retrieval
● Term retrieval
● Video clip retrieval
● Map

6. References
● How The Internet Works(text book)
● Google(http://www.google.co.jp/)
● http://www.seo119.com/measure/system.html
● http://en.wikipedia.org/wiki/Main_Page